This invention is related to storage device for data processing system, especially related to external storage method and its device for micro, handheld and portable data processing systems.
Since the invention of computer, people have been paying close attention to the improvement of computer external storage device, from magnetic drum, magnetic tape to floppy disk and hard disk to exchange, save and backup data and file. For more than a decade, personal computer technology has been improved quickly, but the technology of floppy disk as a removable external storage has no substantial improvement. The only improvement of floppy disk is that the size was reduced from 8 inches, to 5.25 inches, and to 3.5 inches, and the capacity was increased to 1.44 MB. Other than the above improvements, the floppy disk technology stays as what it was ten years ago and there is no further improvement. As we all know, floppy disk has the following disadvantages: small capacity, low speed, easy to be damaged, low reliability. Especially, floppy disk drive is big and heavy. All these disadvantages have caused great inconvenience to users. In the past few years, there are some other storage devices in the market, such as high-capacity ZIP disk, removable optic disc MO etc. These devices have some advantages that floppy disk does not have, such as larger capacity, better reliability than floppy disk, etc. But they still have such disadvantages: big, heavy, requiring physical drive, difficult to carry, complicated to use, requiring external power supply, hard to popularize, high price and so on. Only very small number of computers are equipped with physical drives for such storage devices. In addition, in order to install such an internal drive, you must turn off the computer, open computer casing and find a place in the computer to mount it. Then you need to close the casing, power on your computer and install software driver for the device. You can not use the device until all the above steps have been finished. Obviously, ordinary computer users, even computer specialists may find such storage devices too troublesome to use, not to mention those users who are not familiar with computers.
To sum up, a new kind of computer storage device is urgently needed to replace or complement floppy disk and other external storage device using existing technology. The need is especially urgent for those increasingly popular notebooks and handheld devices. Floppy disk drive and other physical drives, due to their big size and heavy weight, are not suitable for notebooks and handheld devices which must be light, convenient, small and portable. In fact, more and more notebooks don""t have build-in floppy disk drive or CDROM drive for the purposes of compactness and convenience.
Universal Serial Bus (USB) is a new computer technology in recent years. Its standard is defined by some international big companies such as Intel, Microsoft and Compaq etc. The purposes of USB are to make the use of personal computers simpler, easier and faster, and to replace existing serial port, parallel port and keyboard port etc. Today, all Pentium II or above computers (including compatible computers) are equipped with USB. USB has become a new industry standard for personal computer. There may be some other high-speed universal bus standards in the future.
At the time when USB is widely available today, users can no longer tolerate the situation that micro or portable data processing devices can not install built-in floppy disk or other similar storage devices. Users also can hardly tolerate low-capacity, low-speed and vulnerable storage devices like floppy disk, especially can not tolerate the defects that drives for such devices are big and hard to install.
The present invention provides an electronic flash memory external storage method to overcome the shortages of current storage technology. The method uses electronic flash memory, standard universal bus and plug-and-play technology to provide a new external storage device to computer users. All parts and PCB of the external storage device are assembled as a monolithic piece. The high-capacity and high-speed device is simple, light, convenient, portable, easy to use and highly reliable. The invention only uses software to implement external storage functions and can be implemented on different operating system. It is applicable to various data processing systems supporting standard universal bus.
The objects of the present invention are accomplished by the following technical scheme:
The scheme adopts an electronic flash memory external storage method that includes the use of DC power supply and storage media, and has the following characteristics:
said storage media is flash memory, and:
all components and PCB (printed circuit board) used are assembled as a monolithic piece,
said storage method uses software to implement external storage functions (to replace physical drive),
every part is physically at a standstill during the process of access.
Said external storage method involves flash memory and the connecting universal bus interface controller, microprocessor and suspend/resume circuit. The external storage device is connected with data processing system through universal bus interface. The firmware of the external storage device is designed inside the microprocessor. After initialization, the firmware can process standard interface operation requests and special operation requests to the external storage device. After processing the requests, the firmware sends the results back to the requesters. Meanwhile, the driver of the external storage device is implemented and installed in the operating system. The driver is initialized when the external storage device is plugged into host computer. During initialization, the driver instructs upper layer operating system to generate a removable external storage device and assign a corresponding device symbol for it. Afterwards, in response to conventional magnetic disk operation requests, the driver converts these requests into special instructions for the external storage device. The driver then sends the converted instructions to the firmware of the external storage device through bottom layer operating system and universal bus interface control circuit. The firmware executes the instructions and sends results and status back to the driver through the operating system. There are two categories of instructions for the external storage device: read and write. Due to the characteristic that valid data of the flash memory can not be overwritten, a write command is therefore converted into three steps: read, internal erasing, data merge and writing back.
An electronic flash memory external storage device, which comprises storage media and DC power supply, is designed and implemented. All parts and PCB (printed circuit board) used for the external storage device are assembled as a monolithic piece. It uses software to implement external storage functions. The external storage device, including all of its parts, is physically at a standstill during the process of access.
There is an access control circuit on said PCB, which comprises micro-controller, USB interface controller, USB connector and suspend/resume circuit. Said storage media is flash memory. Said micro-controller is connected with USB interface controller, suspend/resume circuit and flash memory respectively. The USB interface controller is connected with USB connector, suspend/resume circuit, flash memory and micro-controller respectively. The USB connector is connected with data processing host machine through USB cable.
Said external storage device is driven by the driver and the firmware. The firmware resides in the microprocessor and the driver is loaded between upper layer operating system and bottom layer operating system of the host computer.
An application example of the external storage device is to utilize it in data processing system. The device is connected with the system through universal bus interface. Driver for the external storage device is installed in the operating system of the data processing system. Under the management of the operating system, users can operate the external storage device the same way operating a classical disk. The driver receives standard disk operation requests from operating system and converts the requests into special instructions for the external storage device. The driver then sends the converted instructions to the firmware through bottom layer operating system and universal bus interface control circuit. The firmware executes the instructions and sends results and status back to the driver through the operating system. Up to this point, the data exchange procedure between the external storage device and data processing system is completed. The recognition procedure of the external device when it is plugged into the host machine includes device plug-in, device registration and allocation of device symbol. The external storage device is plug-and-play without shutting down the host machine when plugging in or pulling out the device.